ALBERT

Beschreibung / Inhaltsverzeichnis: Der exklusive Fotoband zur Jahrhundertexpedition in die Arktis. Im September 2019 legte die Polarstern in Richtung Arktis ab - an Bord das internationale MOSAiC-Forscherteam, das die Auswirkungen des Klimawandels auf das ewige Eis erkundet. Chronologisch aufgebaut dokumentiert der bildgewaltige Band in bisher ungesehenen Fotografien von Esther Horvath Leben und Arbeiten während der einjährigen Reise unter den extremen Bedingungen am Nordpol. Begleitet von kenntnisreichen Essays und Textbeiträgen von Experten, Wissenschaftlern und Expeditionsteilnehmern ist der Band ein eindrucksvolles Zeugnis der wohl größten klimatischen Herausforderung unserer Zeit und bietet Einblicke in dieses einmalige Forschungsprojekt sowie die spektakuläre, schützenswerte Polarlandschaft.

Beschreibung / Inhaltsverzeichnis: Noch nie haben Forschende das Meereis der Arktis so umfassend untersuchen können, wie auf der internationalen MOSAiC-Expedition des Forschungseisbrechers Polarstern. Ein Jahr lang ist das Schiff mit dem Eis durch die zentrale Arktis getrieben; ein Jahr lang haben die Männer und Frauen das Eis mithilfe modernster Technik unter die Lupe genommen. Welche Herausforderungen es dabei zu meistern galt und was sie herausgefunden haben im polaren Hotspot des Klimawandels, erzählen sie in zehn DriftStories, die dieser Band vereint. Faszinierende Arktisforschung zum Anfassen – präsentiert von meereisportal.de.

Beschreibung / Inhaltsverzeichnis: Never before have researchers had the chance to explore the Arctic sea ice as comprehensively as on the international MOSAiC expedition. For an entire year, the research icebreaker Polarstern drifted through the Central Arctic with the sea ice; for an entire year, the men and women of the expedition painstakingly investigated the ice with the aid of cutting-edge technologies. In the ten DriftStories gathered here, they share the challenges they had to overcome, and the discoveries they made in this polar hotspot of climate change: fascinating Arctic research at your fingertips - presented by meereisportal.de.

Beschreibung / Inhaltsverzeichnis: Stratospheric variability is one of the main potential sources for sub-seasonal to seasonal predictability in mid-latitudes in winter. Stratospheric pathways play an important role for long-range teleconnections between tropical phenomena, such as the quasi-biennial oscillation (QBO) and El Niño-Southern Oscillation (ENSO), and the mid-latitudes on the one hand, and linkages between Arctic climate change and the mid-latitudes on the other hand. In order to move forward in the field of extratropical seasonal predictions, it is essential that an atmospheric model is able to realistically simulate the stratospheric circulation and variability. The numerical weather prediction (NWP) configuration of the ICOsahedral Non-hydrostatic atmosphere model ICON is currently being used by the German Meteorological Service for the regular weather forecast, and is intended to produce seasonal predictions in future. This thesis represents the first extensive evaluation of Northern Hemisphere stratospheric winter circulation in ICON-NWP by analysing a ...

Beschreibung / Inhaltsverzeichnis: Anthropogenic climate change constitutes one of the main global crises in the 21st century. It manifests itself distinctly in global warming and its effects. Forests play an essential role in mitigating the effects of climate change, improving our knowledge of the distribution and changes of terrestrial carbon stocks is vital to mitigate its consequences. Therefore, remote sensing is recommended as one of the tools to ensure systematic and operational forest monitoring. Forests in the Russian Federation are of particular importance as it is the most forested country in the world and at the same time, it is the country with the highest uncertainty when calculating global carbon stocks. Remote sensing is recommended as one of the tools to ensure systematic and operational forest monitoring. It can acquire data over large areas with a high repetition rate and at a relatively low cost. In particular, microwave sensors are recommended as they can provide weather and sun independent, systematic observations with high temporal frequency. The main goal of this cumulative dissertation was to develop methods using new algorithms for estimating parameters for boreal forests from remote sensing data acquired with Synthetic Aperture Radar (SAR). Using the SAR data acquired by the sensor with the longest wavelength available at the moment of writing this dissertation in space, the L-band, methods for estimating the above-ground forest biomass were developed. For this purpose, algorithms for machine learning (ML) were applied and validated. These methods were chosen because they are recommended for large data sets and an incomplete theoretical understanding of processes, e.g., the interaction between the forest and the radar signal, and are relatively new in forest monitoring studies. In addition, efforts have been made to establish improved mapping of large-scale forest cover change

Beschreibung / Inhaltsverzeichnis: This book provides a cross-disciplinary overview of permafrost and the carbon cycle by providing an introduction into the geographical distribution of permafrost, with a focus on the distribution of permafrost and its soil carbon reservoirs. The chapters explain the basic physical properties and processes of permafrost soils: ice, mineral and organic components, and how these interact with climate, vegetation and geomorphological processes. In particular, the book covers the role of the large quantities of ice in many permafrost soils which are crucial to understanding carbon cycle processes. An explanation is given on how permafrost becomes loaded with ice and carbon. Gas hydrates are also introduced. Structures and processes formed by the intense freeze-thaw action in the active layer are considered (e.g. ice wedging, cryoturbation), and the processes that occur as the permafrost thaws, (pond and lake formation, erosion). The book introduces soil carbon accumulation and decomposition mechanisms and how these are modified in a permafrost environment. A separate chapter deals with deep permafrost carbon, gas reservoirs and recently discovered methane emission phenomena from regions such as Northwest Siberia and the Siberian yedoma permafrost.

Beschreibung / Inhaltsverzeichnis: Die Hochgebirge haben eine große Bedeutung für das globale Klima, die Wasserversorgung und die Biosphäre. So ist die besonders starke Ausprägung des Amazonas-Regenwalds den Anden zu verdanken. Sie verhindern den Durchzug der aus dem Atlantik mit viel Luftfeuchtigkeit kommenden Wolken. Dadurch erhält das Amazonas-Gebiet im Jahresdurchschnitt über 2.000 mm Regen, was die Grundlage für die intensive Bewaldung ist. Obwohl die Gebirge global nur ca. 12% der Landfläche bedecken, beherbergen Hochgebirge rund die Hälfte aller Säugetierarten und 74% aller endemischen Vogelarten (ohne Inselarten). 21 der 34 globalen Biodiversitätshotspots befinden sich in Hochgebirgen. In den Gebirgen entstehen aufgrund von höheren Niederschlägen wichtige Wasserressourcen auch für die angrenzenden Tiefländer. Trotz der für den Menschen oft erschwerten Zugänglichkeit sind Hochgebirge und Hoch-Plateaus, besonders in tropischen Regionen, Orte dichter Besiedlung und sogar von Hochkulturen. Die Folgen des Klimawandels sind in den Hochgebirgen besonders deutlich. So war die Erwärmung in den vergangenen Jahrzehnten dort höher als in den Flachländern. Die Gletscher schrumpfen in fast allen Gebirgen, insbesondere in den letzten Jahrzehnten. Auf den jetzt eisfreien Flächen siedeln sich schon nach wenigen Jahren neue Pflanzengemeinschaften an. In den Alpen hat das Eisvolumen seit 1850 schon um mehr als zwei Drittel abgenommen. Das entspricht allein seit 1997 einem Süßwasserverlust von etwa dem 14fachen Volumen des Bodensees. Insgesamt sind die Klimaänderungen in den Gebirgsregionen gravierender als im Flachland. Mit der Zunahme der Starkregen und dem Rückgang des Permafrosts nimmt die Gefahr von Erdrutschen zu, und manche Gletscher wurden instabil. Im Mittel haben sich die Temperaturen im Gebirgspermafrost in einem Jahrzehnt von 2007 bis 2016 um etwa 0,2°C erhöht. Die Schneedeckendauer nahm in den letzten Jahrzehnten kontinuierlich ab; die Herausforderungen für den Wintertourismus werden zusehends größer.

Beschreibung / Inhaltsverzeichnis: Der zentralasiatische Naturraum, wie er sich uns heute präsentiert, ist das Ergebnis eines Zusammenwirkens vieler verschiedener Faktoren über Jahrmillionen hinweg. Im aktuellen Kontext des Klimawandels zeigt sich jedoch, wie stark sich Stoffflüsse auch kurzfristig ändern und dabei das Gesicht der Landschaft verwandeln können. Die Gobi-Wüste in der Inneren Mongolei (China), als Teil der gleichnamigen Trockenregionen Nordwestchinas, ist aufgrund der Ausgestaltung ihrer landschaftsprägenden Elemente sowie ihrer Landschaftsdynamik, im Zusammenhang mit der Lage zum Tibet-Plateau, in den Fokus der klimageschichtlichen Grundlagenforschung gerückt. Als großes Langzeitarchiv unterschiedlichster fluvialer, lakustriner und äolischer Sedimente stellt sie eine bedeutende Lokalität zur Rekonstruktion von lokalen und regionalen Stoffflüssen dar.. Andererseits ist die Gobi-Wüste zugleich auch eine bedeutende Quelle für den überregionalen Staubtransport, da sie aufgrund der klimatischen Bedingungen insbesondere der Erosion durch Ausblasung preisgegeben wird. Vor diesem Hintergrund erfolgten zwischen 2011 und 2014, im Rahmen des BMBF-Verbundprogramms WTZ Zentralasien – Monsundynamik & Geoökosysteme (Förderkennzeichen 03G0814), mehrere deutsch-chinesische Expeditionen in das Ejina-Becken (Innere Mongolei) und das Qilian Shan-Vorland. Im Zuge dieser Expeditionen wurden für eine Bestimmung potenzieller Sedimentquellen erstmals zahlreiche Oberflächenproben aus dem gesamten Einzugsgebiet des Heihe (schwarzer Fluss) gesammelt. Zudem wurden mit zwei Bohrungen im inneren des Ejina-Beckens, ergänzende Sedimentbohrkerne zum bestehenden Bohrkern D100 (siehe Wünnemann (2005)) abgeteuft, um weit reichende, ergänzende Informationen zur Landschaftsgeschichte und zum überregionalen Sedimenttransfer zu erhalten. Gegenstand und Ziel der vorliegenden Doktorarbeit ist die sedimentologisch-mineralogische Charakterisierung des Untersuchungsgebietes in Bezug auf potenzielle Sedimentquellen und Stoffflüsse des Ejina-Beckens sowie die Rekonstruktion der Ablagerungsgeschichte eines dort erbohrten, 19m langen Sedimentbohrkerns (GN100). Schwerpunkt ist hierbei die Klärung der Sedimentherkunft innerhalb des Bohrkerns sowie die Ausweisung von Herkunftssignalen und möglichen Sedimentquellen bzw. Sedimenttransportpfaden. Die methodische Herangehensweise basiert auf einem Multi-Proxy-Ansatz zur Charakterisierung der klastischen Sedimentfazies anhand von Geländebeobachtungen, lithologisch-granulometrischen und mineralogisch-geochemischen Analysen sowie statistischen Verfahren. Für die mineralogischen Untersuchungen der Sedimente wurde eine neue, rasterelektronenmikroskopische Methode zur automatisierten Partikelanalyse genutzt und den traditionellen Methoden gegenübergestellt. Die synoptische Betrachtung der granulometrischen, geochemischen und mineralogischen Befunde der Oberflächensedimente ergibt für das Untersuchungsgebiet ein logisches Kaskadenmodell mit immer wiederkehrenden Prozessbereichen und ähnlichen Prozesssignalen. Die umfangreichen granulometrischen Analysen deuten dabei auf abnehmende Korngrößen mit zunehmender Entfernung vom Qilian Shan hin und ermöglichen die Identifizierung von vier texturellen Signalen: den fluvialen Sanden, den Dünensanden, den Stillwassersedimenten und Stäuben. Diese Ergebnisse können als Interpretationsgrundlage für die Korngrößenanalysen des Bohrkerns genutzt werden. Somit ist es möglich, die Ablagerungsgeschichte der Bohrkernsedimente zu rekonstruieren und in Verbindung mit eigenen und literaturbasierten Datierungen in einen Gesamtkontext einzuhängen. Für das Untersuchungsgebiet werden somit vier Ablagerungsphasen ausgewiesen, die bis in die Zeit des letzten glazialen Maximums (LGM) zurückreichen. Während dieser Ablagerungsphasen kam es im Zuge unterschiedlicher Aktivitäts- und Stabilitätsphasen zu einer kontinuierlichen Progradation und Überprägung des Schwemmfächers. Eine besonders aktive Phase kann zwischen 8 ka und 4 ka BP festgestellt werden, während der es aufgrund zunehmender fluvialer Aktivitäten zu einer deutlich verstärkten Schwemmfächerdynamik gekommen zu sein scheint. In den Abschnitten davor und danach waren es vor allem äolische Prozesse, die zu einer Überprägung des Schwemmfächers geführt haben. Hinsichtlich der mineralogischen Herkunftssignale gibt es eine große Variabilität. Dies spiegelt die enorme Heterogenität der Geologie des Untersuchungsgebietes wider, wodurch die räumlichen Signale nicht sehr stark ausgeprägt sind. Dennoch, können für das Einzugsgebiet drei größere Bereiche deklariert werden, die als Herkunftsgebiet in Frage kommen. Das östliche Qilian Shan Vorland zeichnet sich dabei durch deutlich höhere Chloritgehalte als primäre Quelle für die Sedimente im Ejina-Becken aus. Sie unterscheiden sich insbesondere durch stark divergierende Chloritgehalte in der Tonmineral- und Gesamtmineralfraktion, was das östliche Qilian Shan Vorland als primäre Quelle für die Sedimente im Ejina-Becken auszeichnet. Dies steht in Zusammenhang mit den Grünschiefern, Ophioliten und Serpentiniten in diesem Bereich. Geochemisch deutet vor allem das Cr/Rb-Verhältnis eine große Variabilität innerhalb des Einzugsgebietes an. Auch hier ist es das östliche Vorland, welches aufgrund seines hohen Anteils an mafischen Gesteinen reich an Chromiten und Spinellen ist und sich somit vom restlichen Untersuchungsgebiet abhebt. Die zeitliche aber auch die generelle Variabilität der Sedimentherkunft lässt sich in den Bohrkernsedimenten nicht so deutlich nachzeichnen. Die mineralogisch-sedimentologischen Eigenschaften der erbohrten klastischen Sedimente zeugen zwar von zwischenzeitlichen Änderungen bei der Sedimentherkunft, diese sind jedoch nicht so deutlich ausgeprägt, wie es die Quellsignale in den Oberflächensedimenten vermuten lassen. Ein Grund dafür scheint die starke Vermischung unterschiedlichster Sedimente während des Transportes zu sein. Die Kombination der Korngrößenergebnisse mit den Befunden der Gesamt- und Schwermineralogie deuten darauf hin, dass es zwischenzeitlich eine Phase mit überwiegend äolischen Prozessen gegeben hat, die mit einem Sedimenteintrag aus dem westlichen Bei Shan in Verbindung stehen. Neben der Zunahme ultrastabiler Schwerminerale wie Zirkon und Granat und der Abnahme opaker Schwerminerale, weisen vor allem die heutigen Verhältnisse darauf hin. Der Vergleich der traditionellen Schwermineralanalyse mit der Computer-Controlled-Scanning-Electron-Microscopy (kurz: CCSEM), die eine automatisierte Partikelauswertung der Proben ermöglicht, zeigt den deutlichen Vorteil der modernen Analysemethode. Neben einem zeitlichen Vorteil, den man durch die automatisierte Abarbeitung der vorbereiteten Proben erlangen kann, steht vor allem die deutlich größere statistische Signifikanz des Ergebnisses im Vordergrund. Zudem können mit dieser Methode auch chemische Varietäten einiger Schwerminerale bestimmt werden, die eine noch feinere Klassifizierung und sicherere Aussagen zu einer möglichen Sedimentherkunft ermöglichen. Damit ergeben sich außerdem verbesserte Aussagen zu Zusammensetzungen und Entstehungsprozessen der abgelagerten Sedimente. Die Studie verdeutlicht, dass die Sedimentherkunft innerhalb des Untersuchungsgebietes sowie die ablaufenden Prozesse zum Teil stark von lokalen Gegebenheiten abhängen. Die Heterogenität der Geologie und die Größe des Einzugsgebietes sowie die daraus resultierende Komplexität der Sedimentgenese, machen exakte Zuordnungen zu klar definierten Sedimentquellen sehr schwer. Dennoch zeigen die Ergebnisse, dass die Sedimentzufuhr in das Ejina-Becken in erster Linie durch fluviale klastische Sedimente des Heihe aus dem Qilian Shan erfolgt sein muss. Die Untersuchungsergebnisse zeigen jedoch ebenso die Notwendigkeit einer ergänzenden Bearbeitung angrenzender Untersuchungsgebiete, wie beispielsweise den Gobi-Altai im Norden oder den Beishan im Westen, sowie die Verdichtung der Oberflächenbeprobung zur feineren Auflösung von lokalen Sedimentquellen.

Beschreibung / Inhaltsverzeichnis: In the Anthropocene, the thawing of frozen earth due to global warming has drawn worldwide attention to permafrost. Contemporary scientists define permafrost as ground that maintains a negative temperature for at least two years. But where did this particular conception of permafrost originate, and what alternatives existed? The Life of Permafrost provides an intellectual history of permafrost, placing the phenomenon squarely in the political, social, and material context of Russian and Soviet science. Pey-Yi Chu shows that understandings of frozen earth were shaped by two key experiences in the Russian Empire and the Soviet Union. On one hand, the colonization and industrialization of Siberia nourished an engineering perspective on frozen earth that viewed the phenomenon as an aggregate physical structure: ground. On the other, a Russian and Soviet tradition of systems thinking encouraged approaching frozen earth as a process, condition, and space tied to planetary exchanges of energy and matter. Aided by the US militarization of the Arctic during the Cold War, the engineering view of frozen earth as an obstacle to construction became dominant. The Life of Permafrost tells the fascinating story of how permafrost came to acquire life as Russian and Soviet scientists studied, named, and defined it.

Beschreibung / Inhaltsverzeichnis: Die MOSAiC-Expedition verschiebt die Grenzen des Machbaren und markiert einen historischen Meilenstein der Polarforschung. In den Fußstapfen von Fridtjof Nansens bahnrechender Pionierleistung in den Jahren 1893 bis 1896 mit seinem hölzernen Segelschiff »Fram« bringt sie erstmals einen modernen Forschungseisbrecher im Winter in die direkte Umgebung des Nordpols. 20 Nationen haben sich zusammengetan, um die Geheimnisse des dramatischen Klimawandels der Arktis zu entschlüsseln. Untertützt wird das Flaggschiff der Expedition, der deutsche Forschungseisbrecher »Polarstern«, von sechs weiteren Schiffen und Eisbrechern, Flugzeugen und Helikoptern. Insgesamt fünfhundert Menschen nehmen an den verschiedenen Phasen der Expedition teil. Markus Rex, Kopf des Vorhabens und Expeditionsleiter, berichtet anschaulich vom oft genug dramatischen Verlauf dieser Expedition, aber auch von überwältigend faszinierenden Eindrücken aus der Arktis während der langen winterlichen Polarnacht und während des sommerlichen Polartags. Und er beschreibt die unvorstellbaren Herausforderungen, denen sich die Expeditionsteilnehmer eingefroren im polaren Eis gestellt haben - immer geleitet von dem Ziel, Licht in die Prozesse des globalen Klimawandels zu bringen, der nirgends so auseprägt ist wie in der Arktis.

Beschreibung / Inhaltsverzeichnis: This thesis investigates how the permafrost microbiota responds to global warming. In detail, the constraints behind methane production in thawing permafrost were linked to methanogenic activity, abundance and composition. Furthermore, this thesis offers new insights into microbial adaptions to the changing environmental conditions during global warming. This was assesed by investigating the potential ecological relevant functions encoded by plasmid DNA within the permafrost microbiota. Permafrost of both interglacial and glacial origin spanning the Holocene to the late Pleistocene, including Eemian, were studied during long-term thaw incubations. Furthermore, several permafrost cores of different stratigraphy, soil type and vegetation cover were used to target the main constraints behind methane production during short-term thaw simulations. Short- and long-term incubations simulating thaw with and without the addition of substrate were combined with activity measurements, amplicon and metagenomic sequencing of permanently frozen and seasonally thawed active layer. Combined, it allowed to address the following questions. i) What constraints methane production when permafrost thaws and how is this linked to methanogenic activity, abundance and composition? ii) How does the methanogenic community composition change during long-term thawing conditions? iii) Which potential ecological relevant functions are encoded by plasmid DNA in active layer soils? The major outcomes of this thesis are as follows. i) Methane production from permafrost after long-term thaw simulation was found to be constrained mainly by the abundance of methanogens and the archaeal community composition. Deposits formed during periods of warmer temperatures and increased precipitation, (here represented by deposits from the Late Pleistocene of both interstadial and interglacial periods) were found to respond strongest to thawing conditions and to contain an archaeal community dominated by methanogenic archaea (40% and 100% of all detected archaea). Methanogenic population size and carbon density were identified as main predictors for potential methane production in thawing permafrost in short-term incubations when substrate was sufficiently available. ii) Besides determining the methanogenic activity after long-term thaw, the paleoenvironmental conditions were also found to influence the response of the methanogenic community composition. Substantial shifts within methanogenic community structure and a drop in diversity were observed in deposits formed during warmer periods, but not in deposits from stadials, when colder and drier conditions occurred. Overall, a shift towards a dominance of hydrogenotrophic methanogens was observed in all samples, except for the oldest interglacial deposits from the Eemian, which displayed a potential dominance of acetoclastic methanogens. The Eemian, which is discussed to serve as an analogue to current climate conditions, contained highly active methanogenic communities. However, all potential limitation of methane production after permafrost thaw, it means methanogenic community structure, methanogenic population size, and substrate pool might be overcome after permafrost had thawed on the long-term. iii) Enrichments with soil from the seasonally thawed active layer revealed that its plasmid DNA (‘metaplasmidome’) carries stress-response genes. In particular it encoded antibiotic resistance genes, heavy metal resistance genes, cold shock proteins and genes encoding UV-protection. Those are functions that are directly involved in the adaptation of microbial communities to stresses in polar environments. It was further found that metaplasmidomes from the Siberian active layer originate mainly from Gammaproteobacteria. By applying enrichment cultures followed by plasmid DNA extraction it was possible to obtain a higher average contigs length and significantly higher recovery of plasmid sequences than from extracting plasmid sequences from metagenomes. The approach of analyzing ‘metaplasmidomes’ established in this thesis is therefore suitable for studying the ecological role of plasmids in polar environments in general. This thesis emphasizes that including microbial community dynamics have the potential to improve permafrost-carbon projections. Microbially mediated methane release from permafrost environments may significantly impact future climate change. This thesis identified drivers of methanogenic composition, abundance and activity in thawing permafrost landscapes. Finally, this thesis underlines the importance to study how the current warming Arctic affects microbial communities in order to gain more insight into microbial response and adaptation strategies.

Beschreibung / Inhaltsverzeichnis: Recent climate model simulations indicated that sulfate (SO4) formed from ship emissions may be one of the major contributors to the negative anthropogenic aerosol radiative forcing. Due to increasingly stringent regulations on the maximum sulfur content of ship fuels this contribution is expected to decrease strongly in the future. Possibly, nitrate (NO3) formation will compensate for part of the reduction, but measurements indicate that it may be crucial to include coarse mode particle interactions with condensable trace gases in order to quantify this effect. However, none of the aerosol (sub)models previously used for such assessments accounted for the coarse mode particle effects. This provided the motivation to extend one of those submodels, namely MADE, in the present work. The new submodel, MADE3, is based on the second generation of MADE, called MADE-in. It includes nine lognormal modes to represent three size ranges with three types of aerosol particles each. The associated increase in complexity w.r.t. to MADE and MADE-in required a complete revision of the code and careful reexamination of the underlying physical assumptions, as only the fine modes had been considered in the gas–particle interactions in the predecessor submodels. The main new features of MADE3 are the ability of coarse mode particles to take up condensing vapors and to coagulate with fine mode particles, and the gas–particle partitioning of chlorine, which is mainly contained in sea spray (SS) particles. In order to test the algorithms used in the new submodel it was run in a box model setup and the results were compared to those obtained in an analogous setup with the much more detailed, particle-resolved aerosol model PartMC-MOSAIC. The comparison was performed for an idealized marine boundary layer test case and showed improved performance of MADE3 over MADE in the representation of coarse mode particles and total aerosol composition. Subsequently, MADE3 was implemented into the atmospheric chemistry general circulation model EMAC. Due to the new mode structure this required extensive adaptations to other submodels, specifically to the one used for cloud and precipitation processing of aerosol particles. EMAC does not track interstitial aerosol particles separately from those immersed in cloud droplets, ice crystals, or precipitation. Hence, a sophisticated scheme was devised and implemented for the assignment of the in-cloud or in-precipitation aerosol to one of four possible modes, instead of just one possible mode in the MADE case. The coupled model, EMAC with MADE3, was thoroughly evaluated by comparison of simulation output to station network measurements of near-surface aerosol component mass concentrations, to airborne measurements of vertical aerosol mass mixing ratio and number concentration profiles, to ground-based and airborne measurements of particle size distributions, and to station network and satellite measurements of aerosol optical depth. Satisfactory agreement with the observations was obtained and it was thus shown that MADE3 is ready for application within EMAC. The results from an identically designed simulation with the predecessor submodel MADE led to the conclusion that a fraction of the secondary aerosol species partitions to the coarse modes in MADE3 and is thus removed more quickly from the atmosphere. Furthermore, a new evaluation method was developed, which allows for comparison of model output to size-resolved electron microscopy measurements of particle composition. Both submodels, MADE3 and MADE, were finally used in EMAC simulations of the effect of ship emissions on the atmospheric aerosol. As in previous studies for year 2000 conditions, SO4 was found to be the dominant species in the fine modes in this context. In contrast to SO4, the major fraction of ship emissions-induced near-surface NO3 was found to partition to the coarse modes in the MADE3 simulations. A similar amount of fine mode NO3 as in the present and former MADE simulations was also formed. Hence, fine mode particle growth due to ship emissions was also similar, and was reduced in idealized simulations of a future low-sulfur fuel scenario. Particle volume concentration decreased by about 1 % due to ship emissions in the MADE3 simulations, but not in the MADE simulations. This finding was independent of the fuel sulfur content. In summary, the inclusion of coarse mode particle interactions and the gas–particle partitioning of chlorine could alter prior conclusions on the climate effect of ship emissions-induced aerosol perturbations, mainly due to the differences in NO3 formation. This climate effect will be re-quantified in a follow-up study by coupling the MADE3 aerosol to a two-moment cloud microphysics scheme. Further planned applications of the new submodel include the quantification of climate effects of aerosol perturbations via their influence on ice clouds as well as simulations with boundary conditions specific to measurement campaigns. Results from the latter may lead to further model improvements and can also provide guidance for the interpretation of measurement results.

Beschreibung / Inhaltsverzeichnis: Widespread landscape changes are presently observed in the Arctic and are most likely to accelerate in the future, in particular in permafrost regions which are sensitive to climate warming. To assess current and future developments, it is crucial to understand past environmental dynamics in these landscapes. Causes and interactions of environmental variability can hardly be resolved by instrumental records covering modern time scales. However, long-term environmental variability is recorded in paleoenvironmental archives. Lake sediments are important archives that allow reconstruction of local limnogeological processes as well as past environmental changes driven directly or indirectly by climate dynamics. This study aims at reconstructing Late Quaternary permafrost and thermokarst dynamics in central-eastern Beringia, the terrestrial land mass connecting Eurasia and North America during glacial sea-level low stands. In order to investigate development, processes and influence of thermokarst dynamics, several sediment cores from extant lakes and drained lake basins were analyzed to answer the following research questions: 1. When did permafrost degradation and thermokarst lake development take place and what were enhancing and inhibiting environmental factors? 2. What are the dominant processes during thermokarst lake development and how are they reflected in proxy records? 3. How did, and still do, thermokarst dynamics contribute to the inventory and properties of organic matter in sediments and the carbon cycle? Methods applied in this study are based upon a multi-proxy approach combining sedimentological, geochemical, geochronological, and micropaleontological analyses, as well as analyses of stable isotopes and hydrochemistry of pore-water and ice. Modern field observations of water quality and basin morphometrics complete the environmental investigations. The investigated sediment cores reveal permafrost degradation and thermokarst dynamics on different time scales. The analysis of a sediment core from GG basin on the northern Seward Peninsula (Alaska) shows prevalent terrestrial accumulation of yedoma throughout the Early to Mid Wisconsin with intermediate wet conditions at around 44.5 to 41.5 ka BP. This first wetland development was terminated by the accumulation of a 1-meter-thick airfall tephra most likely originating from the South Killeak Maar eruption at 42 ka BP. A depositional hiatus between 22.5 and 0.23 ka BP may indicate thermokarst lake formation in the surrounding of the site which forms a yedoma upland till today. The thermokarst lake forming GG basin initiated 230 ± 30 cal a BP and drained in Spring 2005 AD. Four years after drainage the lake talik was still unfrozen below 268 cm depth. A permafrost core from Mama Rhonda basin on the northern Seward Peninsula preserved a full lacustrine record including several lake phases. The first lake generation developed at 11.8 cal ka BP during the Lateglacial-Early Holocene transition; its old basin (Grandma Rhonda) is still partially preserved at the southern margin of the study basin. Around 9.0 cal ka BP a shallow and more dynamic thermokarst lake developed with actively eroding shorelines and potentially intermediate shallow water or wetland phases (Mama Rhonda). Mama Rhonda lake drainage at 1.1 cal ka BP was followed by gradual accumulation of terrestrial peat and top-down refreezing of the lake talik. A significant lower organic carbon content was measured in Grandma Rhonda deposits (mean TOC of 2.5 wt%) than in Mama Rhonda deposits (mean TOC of 7.9 wt%) highlighting the impact of thermokarst dynamics on biogeochemical cycling in different lake generations by thawing and mobilization of organic carbon into the lake system. Proximal and distal sediment cores from Peatball Lake on the Arctic Coastal Plain of Alaska revealed young thermokarst dynamics since about 1,400 years along a depositional gradient based on reconstructions from shoreline expansion rates and absolute dating results. After its initiation as a remnant pond of a previous drained lake basin, a rapidly deepening lake with increasing oxygenation of the water column is evident from laminated sediments, and higher Fe/Ti and Fe/S ratios in the sediment. The sediment record archived characterizing shifts in depositional regimes and sediment sources from upland deposits and re-deposited sediments from drained thaw lake basins depending on the gradually changing shoreline configuration. These changes are evident from alternating organic inputs into the lake system which highlights the potential for thermokarst lakes to recycle old carbon from degrading permafrost deposits of its catchment. The lake sediment record from Herschel Island in the Yukon (Canada) covers the full Holocene period. After its initiation as a thermokarst lake at 11.7 cal ka BP and intense thermokarst activity until 10.0 cal ka BP, the steady sedimentation was interrupted by a depositional hiatus at 1.6 cal ka BP which likely resulted from lake drainage or allochthonous slumping due to collapsing shore lines. The specific setting of the lake on a push moraine composed of marine deposits is reflected in the sedimentary record. Freshening of the maturing lake is indicated by decreasing electrical conductivity in pore-water. Alternation of marine to freshwater ostracods and foraminifera confirms decreasing salinity as well but also reflects episodical re-deposition of allochthonous marine sediments. Based on permafrost and lacustrine sediment records, this thesis shows examples of the Late Quaternary evolution of typical Arctic permafrost landscapes in central-eastern Beringia and the complex interaction of local disturbance processes, regional environmental dynamics and global climate patterns. This study confirms that thermokarst lakes are important agents of organic matter recycling in complex and continuously changing landscapes.

Beschreibung / Inhaltsverzeichnis: The Yukon Coast in Canada is an ice-rich permafrost coast and highly sensitive to changing environmental conditions. Retrogressive thaw slumps are a common thermoerosion feature along this coast, and develop through the thawing of exposed ice-rich permafrost on slopes and removal of accumulating debris. They contribute large amounts of sediment, including organic carbon and nitrogen, to the nearshore zone. The objective of this study was to 1) identify the climatic and geomorphological drivers of sediment-meltwater release, 2) quantify the amount of released meltwater, sediment, organic carbon and nitrogen, and 3) project the evolution of sediment-meltwater release of retrogressive thaw slumps in a changing future climate. The analysis is based on data collected over 18 days in July 2013 and 18 days in August 2012. A cut-throat flume was set up in the main sediment-meltwater channel of the largest retrogressive thaw slump on Herschel Island. In addition, two weather stations, one on top of the undisturbed tundra and one on the…

Beschreibung / Inhaltsverzeichnis: This book covers the basics of processing and spectral analysis of monovariate discrete-time signals. The approach is practical, the aim being to acquaint the reader with the indications for and drawbacks of the various methods and to highlight possible misuses. The book is rich in original ideas, visualized in new and illuminating ways, and is structured so that parts can be skipped without loss of continuity. Many examples are included, based on synthetic data and real measurements from the fields of physics, biology, medicine, macroeconomics etc., and a complete set of MATLAB exercises requiring no previous experience of programming is provided. Prior advanced mathematical skills are not needed in order to understand the contents: a good command of basic mathematical analysis is sufficient. Where more advanced mathematical tools are necessary, they are included in an Appendix and presented in an easy-to-follow way. With this book, digital signal processing leaves the domain of engineering to address the needs of scientists and scholars in traditionally less quantitative disciplines, now facing increasing amounts of data.

Beschreibung / Inhaltsverzeichnis: This monograph presents a comprehensive synthesis of our current state of knowledge concerning the climate of the Arctic, using the latest meteorological data. All meteorological elements are described in detail for the first time and an up-to-date review of the available literature for each element is given. Climatic regions are distinguished and described. The monograph also provides an account of the present state of research on climate change and variability in the Arctic for three time scales: the Holocene, the last Millennium, and the 20th century. The book concludes with a presentation of the scenarios of the Arctic climate in the 21st century. This monograph is intended for all those with a general interest in the fields of meteorology, climatology, and with a knowledge of the application of statistics in these areas.

Beschreibung / Inhaltsverzeichnis: Finally, the generalized model is scrutinized in terms of its normal, adjoint, optimal and singular modes. It is found that the modes of the empirically modified model are more stable than the ones of the barotropic model. Also the modified barotropic optimal modes are more difficult to excite than their barotropic counterparts. These results are in accordance with previous studies that found that barotropic dynamics may not quantitatively describe LFV. The singular modes of the modified operator have very similar patterns but explain less variance than the barotropic ones. This is consistent with the difficulty in detecting optimal patterns in observations. Finally, we find that the modified barotropic operator is more normal than the classic barotropic one, and thus less variable.